Assesment of factors affecting solar irradiance and development of a model for predictions

Abstract

In Sri Lanka Ceylon Electricity Board plays the role of the system controller by dispatching the energy generated from different power plants to meet the energy demand. Power generation from renewable energy sources such as wind, mini-hydro, solar etc is becoming increasingly popular due to environmental concerns. With the introduction of the net metering system a large number of rooftop solar power systems are getting connected to the national grid. However, it is not possible to predict the energy generation of solar power plants in advance. Therefore, the system controller has no information about the tomorrow’s possible energy availability from these non-dispatchable power plants. Then the only option left with the system controller is to reserve the costly thermal power plants in order to meet the future energy demand. The outcome of this research enables the system controller to predict the possible energy generation from solar power plants based on the weather forecasts. This will provide the system controller with predictions on energy generation and capacity of solar power plants connected to the grid. These predictions will enable to prepare the dispatch schedules accordingly. In this study, the effect of the geographical and meteorological parameters for predicting daily global solar radiation in Sooriyawewa, Hambantota is investigated. A multiple linear regression was applied to explain the relationship among solar radiation and identified geographical and meteorological parameters such as cloud cover, sunshine duration, precipitation, open air temperature, relative humidity, wind speed, gust speed, and sine of declination angle. Variables in these equations were used to estimate the global solar radiation. Values calculated from models were compared with the actual measurements to validate the model. The application of the model to other geographical locations should be carried out as a further study when sufficient data is available for such locations.